Plate tectonics theory describes the large-scale motions of Earth's lithospheric plates and how their interactions explain geological phenomena such as continental drift, seafloor spreading, and mountain building. The theory proposes that Earth's outer layer is divided into tectonic plates that move relative to each other in three main ways - convergent boundaries where plates collide, divergent boundaries where they move apart, and transform boundaries where they slide past each other horizontally.

1. Plate tectonics theory